[Glassman]

Quote:

Originally Posted by hypophysis So this constellation doesn't necessary cause instability. Does anyone with better electronics background have an idea why C14G caused the instability on my amp?

it's a game of phase, that 100p cap is serving as a phase/impedance correction, maybe you have different inductance on the path due to the sockets resulting in different phase behavior..

 

[hypophysis]

Another question:
What problems did you exactly have before bypassing the input resistors on left and right channel with 100pF caps? Did you use a scope to proof the behaviour of the buffers?

Quote:

Originally Posted by Glassman these buffers have whole different input impedance characteristics than Intersils and also the older generation discretes, that's why they're so prone to such problems, however the 100pF cap across the input resistor fixed these problems for me and like you can see for most of us.. loading the outputs with 100R resistors is another way how to get rid of these problems, you might try that if it makes the problem go away.. another interesting try would be removing the 100p cap from ground channel, leaving it only on left & right.. oh and what's your C6 on ground? also try different phones if you can..

 

[rayofsi]

had the same problem as hypophysis

removed the ground c14 and voila the noise is gone.

 

[ppl]

Quote:

Originally Posted by ufokillerz had the same problem as hypophysis removed the ground c14 and voila the noise is gone.

Oh forgot about Glasmans Phase compensation C14 yes this in concert with the allready on board C6G is actualy resulting in too much feedback at High frequencies. You have just discovered what is wrong with too much overall feedback.

 

[motu]

Could someone do a comparison between the different kinds of diamond buffers available? That would be very interesting.

 

[bubbamc119]

Hi guys.
Can I use axial ceramic 100pF capacitors for C14 or does it need to be polypropylene?
Cheers

 

[bg4533]

Quote:

Originally Posted by bubbamc119 Hi guys. Can I use axial ceramic 100pF capacitors for C14 or does it need to be polypropylene? Cheers

I believe that cap is in the signal path. I have always heard ceramic doesn't work the best there. I don't think it will affect stability, just sound.

 

[ljhodad]

Going from the Intersils to the 2nd gens. brought out what I would describe as a more refined sound that enabled more clairity and depth. Re-listening to an Ernie Watts track, I could discern the sound of the sax's valves for the first time. PPA has three OPA627s. Kudos to MisterX for the installation.

 

[Sovkiller]

Quote:

Originally Posted by ljhodad Going from the Intersils to the 2nd gens. brought out what I would describe as a more refined sound that enabled more clairity and depth. Re-listening to an Ernie Watts track, I could discern the sound of the sax's valves for the first time. PPA has three OPA627s. Kudos to MisterX for the installation.

Replace those dark sounding 627's by AD8065 (at least) and you will hear the valves, and the finger tapping them....

 

[bubbamc119]

Just received my kit, thanks bg4533.
A quick question,
In my kit I have 4 blue box type capacitors, I'm assuming these are for the buffer pcb (1 for each buffer, 1 spare). I also have 3 red capacitors (not box type) with '101J PE:' printed on them. Are these the 100pF capacitors to be used for C14 on the PPA board? They look different from capacitors in pics earlier in this thread so I want to make sure.
Thanks guys
Bubba

 

[Glassman]

despite different looks, you are right in your assumptions.. if you look through the last posts here you will realise it is good idea to populate C14 only on left and right channels, leaving one 100p spare..

 

[MisterX]

Quote:

Originally Posted by Glassman despite different looks, you are right in your assumptions.. if you look through the last posts here you will realise it is good idea to populate C14 only on left and right channels, leaving one 100p spare..

That depends on the value of C6.
If C6 = 10pF you are gonna need that cap.
If C6 = 100pF you don't need that cap and installing it will cause problems.

 

[hypophysis]

Quote:

Originally Posted by MisterX That depends on the value of C6. If C6 = 10pF you are gonna need that cap. If C6 = 100pF you don't need that cap and installing it will cause problems.

Any idea if one could do it vice versa - put the cap on the ground channel like on L and R, and leave C6G position unpopulated?

 

[ppl]

Quote:

Originally Posted by hypophysis Any idea if one could do it vice versa - put the cap on the ground channel like on L and R, and leave C6G position unpopulated?

No don't do that

 

[@sia@home]

What would happen if i used these caps for C14 in my PPA with the glassman buffers

Technical/Catalog InformationBC1621-ND
Standard Package2000
CategoryCapacitors
FamilyPolyester Film
VendorBC Components
Capacitance0.1µF
Voltage-Rated63V
Tolerance±10%
SeriesMKT
Package / CaseRadial
PackagingBulk
FeaturesGeneral Purpose
Maximum Temperature105°C
Other NamesBC1621